The present invention relates in general to a bearing mounting method and apparatus to ensure preload control and in particular to a bearing mounting method and apparatus to ensure preload control in face-to-face angular contact paired bearings.
Many naval and marine applications such as pumps require axial stiffness (thrust) control under a variety of operating conditions where the bearing loads are primarily axial loads and often alternate in direction. Duplex ball bearings are usually the designer's choice. Either face-to-face (DF) or back-to-back (DB) mounting arrangements are used with preload built into the bearings by machining surfaces of the bearings and clamping the bearings together in a housing, in the case of DF, or clamping the bearings on the shaft with a lock nut in the case of DB.
There are two major problems with such designs. First, the built-in preload may be significantly increased or decreased due to thermal gradients developed during operation which can overload the bearing or eliminate the original preload. Additionally, because the preload is established by loading one bearing against the other, applied external loads can reduce the load on one of the bearing pair. If a certain thrust load is not maintained on the bearings, ball skidding may result. Ball skidding produces increased noise, surface damage, and higher bearing temperatures. Ultimately, premature failure of the bearing may result.